"Evocative" Martian hills image shows possible goal of rover

By David Brand

Mars Pancam image of the east hills, which are closest to the Mars Exploration Rover Spirit in comparison to other hill ranges seen on the Martian horizon. These hills can be seen in the distance near the left end of the full Mars panorama released Jan. 12. The hills are approximately 2 to 3 kilometers (1 to 2 miles) away from the rover's present location. NASA/JPL/Cornell University Click on the image for a high-resolution version (3756 x 772 pixels, 3026K)

The panorama, composed of a mosaic of five frames across, shows a closer view of the hills closest to the rover Spirit landing site in the Gusev crater. The hills are situated about 2 to 3 kilometers (1 to 2 miles) to the east. Although they would seem to beyond the rover's 600-meter (654 yards) range, Squyres said "we will get as close to them as we can."

Combined images from the orbiting Mars Global Surveyor map the Mars Exploration Rover Spirit's approximate location in relation to nearby craters and hills. Paths to the hills and hill ranges are marked by yellow lines, and the rover is located where the yellow lines intersect. Black arrows locate the east hill complex, a potential rover destination. Click on the image for a high-resolution version (2996 x 4584 pixels, 6234K)

A likely target of the rover, said Squyres, speaking at a press briefing at the Jet Propulsion Lab here, is a crater about 250 meters (800 feet) northeast of the landing site wit a rim 200 meters (about 650 feet) in diameter and 5 meters (about 16 feet) high. Squyres called the crater "an extremely attractive target" because it would "provide a window to subsurface Mars."

The crater is clearly visible in the far left of the 360-degree panorama of the Gusev crater taken by the rover's panoramic cameras, or Pancams, and released yesterday (Jan. 12). All of the Pancam images are being color calibrated in the Cornell Mars Lab in the Space Sciences building on the Ithaca campus, then stitched seamlessly together by a group at JPL working under is Cornell associate astronomy professor Jim Bell, team leader for the Pancams.

Spirit, which is set to roll off its lander onto the Martian surface in the early hours of Thursday morning, was driven for the first time on Monday night (daytime on Mars). Following the cutting of its final umbilical cord connecting it to the lander, it was backed up a few inches, then swiveled in place by 45 degrees, the first step in lining it up with the exit ramp facing west/northwest. Spirit will complete its turn tonight (Jan. 13) then, the following day, travel 3 meters (about 9 feet) down the ramp onto the crater surface, where it will stop for an instrument check. Mission managers say the primary concern is that the vehicle will be rolling off a ramp half as high as the rover itself.

Squyres said that although the terrain around the lander mainly consists of small rocks, "we expect the topography to get more rough, more rugged and more blocky" as the rover approaches the crater. Because the goal of the mission is to find materials that will show if Gusev crater ever contained a lake, he said, finding what lies beneath the surface, as well as material on hills, is essential. "We need a big hole as deep as we can see," he said. The crater is estimated to be 10-20 meters (33 to 66 feet) deep.

At the JPL briefing, mission manager Rob Manning provided the first details of the rover lander's descent onto the planet on Jan. 3. The lander's parachute, he said, opened at 4.6 miles above the surface while the lander was traveling at 920 m.p.h., slowing the descent to 152 m.p.h. The retro rockets fired just 342 feet from the ground and the parachute bridle was released at about 27 feet. The airbags surrounding the lander made 28 bounces over 57 seconds, traveling at 33 feet a second. The landing site is less than 330 yards from the first bounce.

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